Lubricating oils containing metal derivatives of cyclic imides



Patented Feb. 17, 1953 I LUBRIGATING OILS CONTAINING METAL DERIVATIVESor c clic nnncs John R. Morris, Fishkill, and James R; Roach, Beacon, N.Y., assignors to The Texas Company. New York, N. Y., a corporation ofDelaware No Drawing Application'June 27, 195-1,

. serial No. 233,942

6.Glaims- (o1. aria -49.7) r

I case lubricants in internal combustion engines tend to oxidize at thehigh temperatures to which they are subjected in this type of servicewith the formation of gums and sludges, which clog the oil feed linesand form varnish-like deposits on the surfaces of rings, pistons,cylinders and other engine parts. Such deposits decrease the efficiencyof operation of the engine and.- eventually lead-to piston sticking andscoring of the cylinder walls. Y

It is common practice to add to crankcase oils small amounts ofso-called detergents, which hovel-he p oper y of r ng h s formation ofsludges and varnishes, Various types of metal organic compounds areknown to be effective for this Purpos particularly thos compounds wherent metal is linked to an organic group through an oxygen atom. Forexample, Davis ct al. in U. S. Patent No 2,335,261 disclose thatpolyvalent metal salts of high molecular weight fatty acids such as waxacids and alkyla d aromatic acids such as alkylatecl benzoic andphthalic acids are eff ive for this purpose Th metal phenates,particularly the polyvalent metal h na es. a isclosed for example byGardiner glutaric acids, having aliphatic substituent groups et al in UvS. Patents No. 2,228,661 and No, 7

However, c mpou s of th above type have the disadvantage hat th y areuns able in the pres nc of Water. so that th y hydro yze with theformation or water soluble metal compounds r sludg as Well as. iactionale corrosive maerials. The detergen mpounds thus become d s royed orremoved from the lubricating com p sition when th l r becomes contaminaed with water, such as may occur n hand ng a d in storage.

In c rdance with ourinvention lubricating oils having superior detereeny and stability, suitable for use as crankcase oils in automotive.diesel and airpla e en ines, are pr duced by adding to minerallubricating oils small amounts of compounds of the class consisting ofoilsoluble metal cyclic imilles derived irom aliphatic liicarboxylicacids. Su table compounds 01 this type are metal derivati es oi stablecyclic'imides,

of suflicient size to impart oil solubility to the molecule. We havefound that compounds of this class wherein. a metal is linked directlyto a nitrogen atom positioned between two acyl groups possess excellentdetergency and anti -sludging properties in mineral lubricating oils,and are furthermore. characterized by a remarkable stability andresistance to hydrolysis as compared with the corresponding compoundscontaining the metal motion linka e which have been employed heretoforein'lubricatlng oil to promote engine cleanliness. They are particularlyValli able for use in producing lubricating oils to meet the severerequirements of airplane engine oils.

The preferred comp unds employed as lubrieating oil additives ac ordingto our vention may be repr sented by the general-formula Rice-00 moo, s-M Ba- O(.) H I 11 wherein M is a metal, a is an integer equal to thevalency of, the metal, R is a methylene group, n

is 1 or 0, and R1, R2 and R are members of: the group consisting ofhydrogen and aliphatic hy= drocarbon groups, at leastone of them beingan alkenyl or alkyl group containing from about .15

to about 30 carbon atoms. and most suita y from about 18 to 25 carbonatoms. M of the formula may be any alkali metal, alkaline earth metal orother metal ca ble of forming compounds of this type, as for ex mplesodium, potassium, lithium calcium, barium, strontium. magnesium,-a1-uininum; tin, zinc cobalt, nickel, titanium r man anese. It ispreferably a polyvalent metal. The bivalent metals, particularly zincand mag: nesium, are especially uitable,

As suitable examples of the above class of comipounds may be mentionedmag esium docosenyl succinimide, calcium qocosenyl glutarimicle, zinc amethyl-p-pentadeceny1 succinimide, co baltous nondecenyl glutarimide,calcium penta: cosenyl succinimide, titanous a-propyl-fl-eicosenylsuccinimide, a'ndSO forth.

.lhe above described imide derivative may e employed varying amountsdepending upon the'characteristics oi the lubricating oil and the cnditions under which his to be employed.

Even in very small amounts, as about 0.01 per cent by weight, theyimpart substantial improvement in the detergency characteristics ofmineral lubricating oils. Ordinarily they are employed in crankcase oilsin amounts within the range of from about 0.5 to about 5 per cent byWeight, and preferably with the range of from about 0.5 to about 3 percent by weight of the composition.

The metal imides of this invention are formed by treating aliphaticsubstituted succinimides and glutarimides with metal compounds underconditions such that the hydrogen atom of the imido group is replaced bymetal. The aliphatic substituted succinimides and glutarimides mayconveniently be obtained by reacting the anhydrides of maleic,glutaconic, citraconic, homomesaconic, or itaconic acids, or homologuesthereof, with unsaturated aliphatic hydrocarbons, and then convertingthe aliphatic-substituted anhydrides obtained to the correspondingimides by treating with ammonia. V Alkenyl substituted anhydrides, whichare obtained when olefinic anhydrides are reacted with olefin polymers,may be hydrogenated if desired either before or after conversion to theimides to obtain the corresponding alkyl substituted compounds.

In forming the polyvalent metal salts the imide may be treated. directlywith a suitable compound of the polyvalent metal or the imide may befirst treated with an alkali metal compound and the alkali metal imidederivative then converted to the polyvalent metal derivative by doubledecomposition with a suitable polyvalent metal compound.

The following examples illustrate the preparation of these metal imidederivatives by each of the above methods.

EXAMPLE 1 The magnesium derivative of an alkenyl succinimide wasprepared by the following procedure: An alkenyl succinic anhydride wasfirst from 100 C. to 240 C. and the heating then con- 'tinued for hourlonger without the introduction of ammonia. The product was taken up inether and washed free of excess ammonia, the ether stripped out and theproduct dried by adding toluene and again stripping to remove the ftoluene and water. 405 grams of the alkenyl succinimide thus obtainedwere dissolved in toluene and a solution of magnesium methylate obtainedby dissolving 12.4 grams of magnesium metal in dry methanol added. Themixture was heated under reflux for 18 hours and the solvent strippedoil. 417 grams of product were obtained analyzing 3.10% magnesium and3.44% of nitrogen, as compared with the theoretical values 3.00% and3.48%, respectively, for magnesium alkenyl (C21) succinimide.

EXAMPLE 2 The zinc derivative of an alkenyl succinimide was prepared asfollows. An alkenyl succinimide was prepared as described in Example 1,employing in the alkylation of the maleic anhydride a propylene polymerhaving a molecular weight corresponding to 21 carbon atoms per molecule.324 grams of the alkenyl succinimide thus obtained were added to asolution of sodium methylate obtained by dissolving 19.2 grams of sodiummetal in methanol, and the reaction mixture refluxed for two hours. 52grams of zinc chloride dissolved in methanol were then added and themass stirred for four hours, the alcohol stripped out and the residuetaken up in ether and Washed with water until the wash water was free ofchlorine. The ether was then stripped out and the product dried byadding toluene and again stripping. 338 grams of product were obtainedwhich analyzed 9.82% of ash as compared with the theoretical value of9.63% of zinc oxide for zinc alkenyl (C21) succinimide.

The compounds obtained as described in the above examples wereoil-soluble and water-stable and possessed outstanding properties withregard to detergency and an-ti-sludging properties in lubricating oils.Table I below shows test data obtained on the magnesium alkenylsuccinimide obtained as described in Example 1.

l A different base oil giving only 304 mg; of deposit was used in thistest.

The water stability test of the above table is carried out in thefollowing manner: 200 grams of oil containing additive and 200 grams ofdistilled water are stirred together for 15 minutes at room temperatureby means of a Mixmaster running at 700 R. P. M. The emulsion is thencentrifuged and an ash determination made on the clarified oil. The percent of additive removed is calculated from the difference between theash content of this washed sample and that of the original oil.

The carbon black dispersion test of the foregoing table is a bench testdesigned to show the detergency characteristics of an oil. The test iscarried out in the following manner: A ml. portion of a suspensionprepared by thoroughly mixing 1 gram of carbon black into a solutionconsisting of grams of the test oil and 150 grams of kerosine is placedin a centrifuge tube and centrifuged at 2000-2100 R. P. M. for 5minutes. About 35 m1. of the centrifuged suspension is immediatelypoured from the top of the centrifuge tube and a 5 ml. portion of thistaken and diluted to 60 ml. with kerosine in a tall bottle or Nesslertube. The sample thus prepared is compared visually with a series ofgraduated standards containing various amounts of carbon black suspendedin a similarly diluted oil of the same character as the test oil. Thedispersion value of the test oil is expressed in terms of arbitrarynumbers assigned to these standards on the basis of the relative amountsof suspended carbon which they contain. This test measures specificallythe ability of an oil to hold in suspension or dispersion carbon black,which may be considered comparable to blow-by carbon in an internalcombustion engine, and it ga e-m also provides Ia generally good.indication of the oil-ringsludging characterof an oil inservice.

The high temperature depositsv test- .of the table is also a bench testwheren an aluminum cylinder one inch in diameter and three inches longis repeatedly dipped-into a beaker containing a sample of the test .oilmaintained at 525 F. for a period of 20 hours. The depositremaining onthe test specimen .after washing with pentane and drying is determined.

As shown in Table I, the magnesium alkenyl succinimide was highlyeffective in dispersing carbon black and in reducing varnish-formationin a mineral lubricating oil at high temperatures.

1 It was markedly superior in these tests indicating the ability of anoil to maintain engine cleanliness in comparison with magnesium alkylphenolate, which is considered to be one of the most efiective compoundsemployed for this purpose at the present time. In addition the compoundof our invention has a satisfactory degree of water-stability, equal toover three times that of the phenolate. The improved water-stability ofthis compound is in agreement with tests performed on another typicalcompound of this class wherein barium alkenyl succinimide was heated foran hour in sulfuric acid without substantial change.

The detergency characteristics of compounds prepared as described inExamples 1 and 2 were further determined by means of the C. F. R.

I high speed engine test, which is a test for determining the ability ofan oil to reduce engine deposits under severe operating conditions. Thistest is carried out with a standard C. F. R. single cylinder internalcombustion engine operating under the following conditions:

Compression ratio 6.5:1. Speed, R. P. M. 1300. Air/fuel ratio 13:1.

7 Jacket temperature 285 F.

Oil in temperature 185 F.

Oil out temperature 200 F.

Fuel 100 octane (minimum) aviation type containing 4 cc. TEL/gal.

Duration of run 50 hours.

At the termination of each run, electrical measurements are taken of thepiston skirt deposit with respect to the extent or percentage of surfacearea of the piston skirt which is covered by the lacquer deposit as wellas the average thickness of the deposit. The carbonaceous deposits inthe piston ring grooves are also carefully scraped oil and weighed.Extensive laboratory testing has shown that a crank case lubricating oilwhich will markedly reduce the tough black lacquer deposit on the pistonskirt and the carbonaceous deposits occurring in the ring belt area, canbe expected to reduce deposits at all points where high temperatures areencountered. The tests listed are therefore an accurate indication ofthe engine cleanliness of the oil compositions under test.

The following table gives the results obtained in the above test on anoil containing small amounts of our compounds as compared with the baseoil alone, which was a highly refined residual lubricating oil from aparafiin base crude employed as an airplane engine lubricating oil. Themagnesium alkenyl succinimide of the table is that prepared as describedin Example 1. The zinc alkenyl succinimide was prepared as described inExample 2 except that a propylene Table 11' c. F. R. HIGH srn'a'n ENGINErrns'rs Piston Skirt Deposit Additive l Percent Thickness Covered 'In.10-

None (Base oil) 2. 0 1% Mg alkcnyl succinimide 0.5% Zn alkenylsuccinimidc -0. 0 '0. 0

The data given in Table II show the outstanding properties of ourcompounds in reducing engine deposits in an actual engine test. In thistest an oil was produced by the use of small amounts of typicalcompounds of our invention which gave zero engine deposits after 50hours of severe operating conditions corresponding to those encounteredin airplane engine lubrication, as compared with heavy varnish depositscovering per cent of the piston skirt obtained with the uninhibited baseoil under the same conditions.

Lubricating compositions containing the additives of our invention mayalso contain other additives such as are ordinarily employed inlubricants, such as oxidation inhibitors, pour point depressors,viscosity index improvers, corrosion inhibitors, and so forth, as wellas other detergents such as metal phenates, sulfonates and other metalsalts- Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations ficient toimprove the detergency thereof of a compound of the general formula HR1C-CO Rim N- M B3 CO wherein M is a polyvalent metal, a: is an integerequal to the valency of the metal, R. is a methylene group, n is 1 or 0,and R1, R2 and Re are members of the group consisting of hydrogen andaliphatic hydrocarbon groups, at least one of them being an aliphatichydrocarbon group containing from about 15 to about 30 carbon atoms.

2. The lubricant according to claim 1 wherein the metal is a divalentmetal.

3. A lubricant consisting essentially of a refined minerallubricatingoil and about 0.1 to about 5 per cent by weight of the magnesium salt ofa succinimide substituted on one of its methylene groups by an aliphatichydrocarbon group containing from about 15 to 30 carbon atoms.

4. A lubricant consisting essentially of a refined mineral lubricatingoil and about 0.1 to about 5 per cent by weight of the zinc salt of asuccinimide substituted on one of its methylene groups by an aliphatichydrocarbon group containing from about 15 to 30 carbon atoms.

5. A lubricant consisting essentially of a refined mineral lubricatingoil containing about 0.5 to 3.0 per cent by weight of magnesium alkenyl(C1540) succinimide and about 0.5 to 2.0 per cent by weight of zincalkenyl (Cm-30) succinimide.

6. A lubricant consisting essentially of a refined mineral lubricatingoil containing from about 0.1 to about 5 per cent by weight of a mixtureconsisting of a magnesium salt of a succinimide substituted on one ofits methylene groups by an aliphatic hydrocarbon group containing fromabout 15 to about 30 carbon atoms and a zinc salt of a succinimidesubstituted on one 10 of its methylene groups by an aliphatichydrocarbon group containing from about 15 to about 30 carbon atoms.

JOHN R. MORRIS. JAMES R. ROACH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,363,516 Farrington Nov. 28,1944 2,417,833 Lincoln Mar. 25, 1947 2,458,425 Rocchini Jan. 4, 19492,490,744 Trlgg Dec. 6, 1949

1. A LUBRICATING CONSISTING ESSENTIALLY OF A REFINED MINERAL LUBRICATINGOIL AND A SMALL AMOUNT SUFFICIENT TO IMPROVE THE DETERGENCY THEREOF OF ACOMPOUND OF THE GENERAL FORMULA